Impacts of preharvest sprays of fulvic acid on some quality and antioxidant properties of grapes the Fakhry Cultivar (Vitis vinifera cv Fakhri)

The excessive use of chemical fertilizers has caused a lot of environmental problems, so the use of organic and humic compounds, especially fulvic acid, has been considered in the production of horticultural crops. This research was carried out to evaluate the effect of foliar application of fulvic acid on quality and antioxidant properties of grapevine cv. Fakhri at four levels (0, 2.5, 5 and 10 g/l) using a randomized complete block design with three replications. Grapes were cultivated in a traditional traning system. The vines were sprayed at three stages: 1- Berry formation, 2- Lag phase, 3- Veraison. After harvesting, (Brix 20) qualitative and antioxidant properties of fruits were evaluated. Results of the experiment showed that 2.5 g/l of fulvic acid significantly increased soluble solids, vitamin C, soluble sugars, total phenol, antioxidant capacity of fruits, chlorophyll and leaf potassium content while 10 g/l of fulvic acid increased only titratable acidity of fruits. With increasing fulvic acid concentration evaluated traits decreased, so that 10 g/l fulvic acid did not show significant effect on improving qualitative and antioxidant properties of fruits. Application of fulvic acid did not show significant effect on fruit flavonoid, and carotenoid, phosphorus and nitrogen contents of leaves. As final result, fulvic acid treatment had an important effect on improving the qualitative and antioxidant properties of Fakhri cultivar and 2.5 g/l had the highest effect which is recommended to be considered as a best concentration.